In UNIX-style permissions, which chmod octal sets: owner = read/write/execute, group = read/execute, others = read/execute?

Introduction / Context:
File permissions on UNIX and Linux systems are commonly set using octal notation with chmod. Each digit represents a triad of permissions (read, write, execute) for owner, group, and others. Mastering octal mappings streamlines secure defaults for scripts, binaries, and web content.

Given Data / Assumptions:

• Desired permissions: owner = rwx, group = r-x, others = r-x.
• Octal mapping: r=4, w=2, x=1 per position.
• Order: owner, group, others.

Concept / Approach:

Compute each triad: owner rwx = 4+2+1 = 7; group r-x = 4+0+1 = 5; others r-x = 4+0+1 = 5. Concatenate digits as owner/group/others to obtain 755. This is a common setting for executable scripts and directories where users should traverse but not modify.

Step-by-Step Solution:

Verification / Alternative check:

Command example: chmod 755 file then verify with ls -l, which should display -rwxr-xr-x for a regular file.

Why Other Options Are Wrong:

• 000: no permissions at all.
• 744: group/others are read-only (r--), not r-x.
• 555: everyone read/execute; owner lacks write.
• None of the above: incorrect because 755 matches exactly.

Common Pitfalls:

• Confusing symbolic (u=rwx,g=rx,o=rx) with octal forms.
• Setting directories to 644, breaking traversal; directories need execute to enter.

Final Answer:

755.